Conventionally, there are known to be electric organs that include multiple tone wheels. A tone wheel is a gear-shaped member. That is, a tone wheel is such that multiple recesses and protrusions are formed on the circumferential surface of a disc-shaped member. The number of recesses and protrusions corresponds to the pitch. An electric organ includes electromagnetic pickups that are arranged so as to oppose the respective circumferential surfaces of the tone wheels. When the multiple tone wheels are rotated by a motor, the magnetic fields around the electromagnetic pickups change periodically due to the rotation. Electric signals corresponding to the changes in the magnetic fields are output from the electromagnetic pickups. The electric signals are amplified by amplifiers and are output from output terminals.
In the electric organ, basically, nine drawbars (slide switches including multiple contact points) are mounted, and a fundamental tone (8′), a second harmonic (4′), a third harmonic (2−⅔′), a fourth harmonic (2′), a fifth harmonic (1+⅔′), a sixth harmonic (1+⅓′), an eighth harmonic (1′), a tone that is an octave lower than the fundamental tone (16′), and a third harmonic of 16′ (5+⅓′) are respectively allocated to the drawbars. Note that “′” means “feet” (unit expressing the length of a pipe of a pipe organ). When one key of the electric organ is pressed, the fundamental tone corresponding to that key and the other eight harmonics thereof are simultaneously output. The above-described drawbars are operators for adjusting the volumes of the fundamental tone and the harmonics. In other words, the drawbars are operators for setting the timbre.
Also, conventionally, a rotary speaker is known as a speaker that is used when reproducing an output signal of an electric organ. A rotary speaker includes a speaker unit that is fixed in an upward or downward orientation, and a rotor (horn) that rotates about a rotational axis extending in the vertical direction above or below the speaker unit and causes the sound emission direction to rotate. Thus, by rotating the sound emission direction, auditory effects (chorus, tremolo, etc.) are applied to the reproduced sound. A rotary speaker is configured such that the rotation speed of the rotor can be selected. For example, upon setting a rotation speed selection switch to “FAST”, the rotor rotates at about 400 rpm. On the other hand, upon setting the rotation speed selection switch to “SLOW”, the rotor rotates at about 50 rpm. Also, when the rotation speed is switched from “FAST” to “SLOW” or from “SLOW” to “FAST”, the rotation speed of the rotor gradually changes.
Conventionally, various electronic musical instruments capable of imitating the effect obtained using such a rotary speaker have been proposed. For example, the electronic musical instrument proposed in Patent Document 1 (Japanese Patent Application Laid-Open Publication No. 2003-058159) stores waveform data expressing the waveform of an output signal of an electric organ. The waveform data expresses a sound in state prior to the effect of the rotary speaker being applied thereto. The electronic musical instrument sequentially reads out sample values constituting the waveform data to reproduce a signal similar to the output signal of the electric organ. Here, the electronic musical instrument includes a modulation circuit that modulates the reproduced signal. Using the modulation circuit, this electronic musical instrument can reproduce a signal to which an effect similar to the effect obtained using the rotary speaker is applied.
Also, for example, the electronic musical instrument proposed in Patent Document 2 (Japanese Patent Application Laid-Open Publication No. H07-181970) stores impulse responses at rotation angles of a rotor of a rotary speaker. The impulse responses are measured as follows. First, an impulse signal is input to an input terminal of the rotary speaker in a state in which the rotor faces forward. The reproduced sound is sampled using a microphone placed in front of the cabinet of the rotary speaker. Next, an impulse signal is input to the input terminal of the rotary speaker in a state in which the rotor has been rotated by a predetermined minute angle. The reproduced sound is sampled using the microphone. Thereafter, the task of measuring and recording the impulse response each time the rotor is rotated by the predetermined minute angle is repeated until the rotor has performed one rotation about the rotation axis. Also, similarly to the electronic musical instrument disclosed in Patent Document 1 described above, this electronic musical instrument sequentially reads out sample values constituting waveform data to reproduce a signal that is similar to the output signal of the electric organ. This electronic musical instrument selects one impulse response among the multiple impulse responses according to the rotation angle of the rotor. Then, the electronic musical instrument outputs a signal obtained by convoluting the reproduced signal and the currently-selected impulse response. Accordingly, it is possible to output a signal to which an effect similar to the effect obtained using the rotary speaker has been applied.
However, with the electronic musical instrument disclosed in Patent Document 1 described above, the modulated signal of the modulation circuit is relatively simple, and therefore it is difficult to reliably imitate the effect obtained using the rotary speaker.
Also, with the electronic musical instrument according to Patent Document 2 described above, the load of the convolution calculation is high, and therefore a calculation device with a high processing ability is used, which causes the component cost to increase.